The Fei Xing San Jie Tong Wei Nei Si Miao Jing 太上洞玄灵宝飞行三界通微内思妙经

It is one of the ancient Numinous Treasure Scriptures of Taoism, probably compiled during the Southern and Northern Dynasties or the Sui and Tang dynasties.

This text is quoted in Imperial Readings of the Taiping Era (Volume 676) and also recorded in Jiang Shuyu’s Catalogue of Scriptures for Pacifying and Establishing Altars.

Consisting of one scroll, it is included in the Taiping Section of the Daoist Canon.

The scripture is pseudonymously attributed to the Supreme Ultimate True Person (Xu Laile), who expounds the "Supreme Numinous Treasure Supreme Way of Concealed Existence and Flying Through the Three Realms".

This method belongs to the practice of inner contemplation: one is required to tap the teeth and recite incantations in accordance with the ritual on specified days and times, while mentally contemplating the essences of the sun, moon, stars and constellations, or the various gods within one’s own body.

It is said that practicing this method for a hundred days can cure all illnesses; practicing for three hundred days enables one to command ghosts and gods and soar into the void; practicing for three years allows one to attain the Dao and become a true immortal; and practicing for five years elevates one to the rank of Immortal King.